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ATPL POF > High Speed Flight + contamination > Flashcards

High Speed Flight + contamination Flashcards

1
Q

What is the equation for local speed of sound

A

LSS = 39squarerootk

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2
Q

What is the equation to work out the Mach number

A

Mach number = TAS / LSS

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3
Q

In subsonic flight describe the Mach. Numbers

A

All local Mach numbers are below 1

For low subsonic Mfs = <0.4

For high subsonic Mfs = >0.4

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4
Q

Describe transonic Mach numbers

A

Somewhere

Ml <1
Ml = 1
Ml >1

Somewhere in transonic region Mfs = 1

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5
Q

Describe supersonic Mach numbers

A

All local Mach numbers >1

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6
Q

What is Mcrit

A

The free steam Mach number which somewhere on your aircraft you have a local flow of Mach 1

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7
Q

What is Mdet

A

Mach detachment speed

Measures as free stream

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8
Q

Where do normal shockwaves occur

A

In the transonic region

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9
Q

Can air flow normally through a normal shockwave

A

Yeh

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10
Q

What speed is the airflow infront of the normal shockwave

A

Supersonic

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11
Q

What speed is the airflow behind the normal shockwave

A

Subsonic

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12
Q

If the air infront of the normal shockwave is 10% above Mach 1 what is the air behind the shockwave like

A

10% below Mach 1

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13
Q

How thick is the normal shockwave

A

0.0025mm

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14
Q

What is the most violent shockwave

A

Normal shockwave

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15
Q

What shockwave creates the most drag

A

Normal shockwave

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16
Q

What does a shockwave do to temperature and density

A

Temperature increases (energy comes from total pressure decrease)

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17
Q

When do oblique shockwaves occur

A

At a higher speed than normal shockwaves

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18
Q

If the speed of the airflow is above Mach 1 infront of the oblique shockwave what speed it is behind

A

Above Mach 1 but slower

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19
Q

Does the oblique shockwave change direction of the airflow

A

Yes it does

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20
Q

What creates a bow wave

A

Normal shockwave
+
Oblique shockwave

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21
Q

What happens to the bow wave as speed increases

A

Stagnation point (which creates the normal wave) decreases and eventually the bow wave attaches to leading edge creating just a oblique wave

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22
Q

At what speed does the bow wave attach or detach from the leading edge

A

Mdet

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23
Q

What shockwave do we feel / creates the sonic boom we hear

A

Oblique shockwaves

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24
Q

How does speed affect the oblique shockwave

A

Faster we go the more pushed back they become

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25
Q

How does speed affect the Mach cone

A

Faster you go the smaller the Mach cone around aircraft

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26
Q

What is the Mach cone angle

A

Angle between flight path and the oblique shockwaves

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27
Q

What is the equation for the Mach cone angle

A

Sin angle= LSS/TAS

Or

= 1/Mach n

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28
Q

What is the expansion wave

A

NOT A SHOCKWAVE

Air curving round a surface

Speed or air flow in an expansion increase

Temp decreases

Density decreases

Pressure / energy the same

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29
Q

What happens to Mach number when you go into warmer air

A

Constant Mach number

Temp ^

Density down

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30
Q

What is chicken tikka masala

A

In tropopause = chicken. Tikkamasala

In isotherm = chicken masala tika

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31
Q

What happens to AOA as you climb at high speed on constant Mach

A

Increases (small increase)

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32
Q

What happens to flight path angle if you’re climbing at high speed on a constant Mach

A

Decreases

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33
Q

What happens to pitch as you’re climbing on a constant Mach at high speed

A

Decreases

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34
Q

What happens to AOA as you’re climbing on a constant CAS at high speed

A

Remains constant

35
Q

What happens to flight path angle as you climb at a contact CAS

A

Decreases

36
Q

What happens to pitch at you climb at a content CAS

A

Decreases

37
Q

What happens to AOA as you descent on a constant Mach

A

Decreases

38
Q

What happens to flight path angle as you descend on a constant Mach

A

Increases

39
Q

What happens to pitch angle as you descend on a constant Mach

A

Decreases

40
Q

What happens to AOA
Flight path angle
And pitch angle when descending on a constant CAS

A

Remain constant

41
Q

What is Mcrit

A

The free stream Mach number at which somewhere on the aircraft reaches Mach 1

Assuming load factor of 1

42
Q

How does a thick wing affect Mcrit

A

Lower Mcrit

43
Q

What happens above Mcrit

A

A normal shock wave is formed

44
Q

As you increase speed up to what point does the cp keep moving rearwards

A

Just before Mach drag divergence

45
Q

What happens when separation for normal shockwaves occurs at the trailing edge for both upper and lower normal shockwaves

A

Most drag

46
Q

What happens when normal shockwave transforms into an oblique wave

A

Centre of pressure shoots back to 50%

47
Q

What happens at Mach 1 Mfs

A

Normal shockwaves attach to trailing edge and also a bow wave forms

48
Q

Life of a shockwave

A

See notes in jotted = can’t type it well

49
Q

Describe the pressure distribution when there is oblique waves at the trailing edge and a bow wave at the leading edge

A

Uniform pressure distribution over the wing

50
Q

When is a aircraft super sonic

A

After Mdet

51
Q

When is the Mach drag divergence

A

Just beyond Clmax

52
Q

When is the worst Cl/Cd ratio for high speed flight

A

Mfs 1

53
Q

What happens when the cp shoots aft in high speed flight

A

Pitch forward = Mach tuck

Aircraft needs a Mach trimmer

= needs all moving tailplane

54
Q

What happens to stick force gradient after Mcrit

A

Stick force gradient becomes neutral (doesn’t get harder to move with height)

After even more speed increase eventually becomes negative

55
Q

What is the aerodynamic ceiling

A

At this height any increase / decrease in speed results in stall or shock stall

56
Q

What is the buffer margin

A

A range of speeds below the ceiling to ensure u don’t stall and to allow for turbulence / disturbance

57
Q

What does aerodynamic ceiling reduce with

A

Anything that increases stall speed

58
Q

What is the manoeuvre ceiling

A

Aerodynamic ceiling adjusted for the ability to manoeuvre

59
Q

How does thickness to chord ratio affect Mcrit number

A

High thickness to chord ratio = lower Mcrit number

60
Q

What is a super critical wing

A

Large radius leading edge

Flatter upper surface

Both negatively and positively cambered aerofoil

Better for high speed flight than a normal wing of similar thickness to chord ratio

61
Q

How does sweep back wings affect Mcrit

A

Increases effective chord length

Reduces thickness to chord ratio

Increases Mcrit

62
Q

What can you put infront of the usually places for separation to occur due to shockwaves

A

Vortex generators

63
Q

What is wave dependant on

A

Surface area (cross sectional area)

64
Q

How can you reduce wave drag

A

Area ruling

Intending the fuselage for wings to reduce cross sectional area

65
Q

What are the disadvantages of s supercritical aerofoil

A

can produce rapid and unpredictable movement of the separation point

Poor low speed handling

Large nose down pitching moment because majority of lift occurs in the rear 30% of wing

Isn’t practical wing shape for root which makes installation of trailing edge devices difficult

66
Q

What happens to Mcrit when you sweep back a wing

A

Effective chord longer = reduces thickness - chord ratio = increases Mcrit

67
Q

What is airframe contamination

A

Anything that is going to change the surface of the aircraft

68
Q

Where is frost most likely to form on a aircraft

A

Under the wing due to cool fuel

Brush off or de-ice

69
Q

What airspeed does frost not tend to form above

A

250knots

70
Q

Where does snow form inflight usually

A

Stagnation points

Leading edges

71
Q

What airspeed does rime ice not tend to form over

A

250 knots

72
Q

How can you get rid of rime ice

A

Warming leading edge

Or

Inflatable boots (however they need to let ice build up first)

73
Q

What aircraft is most at risk from clear ice

A

Turbo props as they usually fly in the altitudes associated with it

74
Q

What effect does contamination have on drag

A

Skin friction drag increase

Increased weight = induced drag increase

75
Q

What thickness aerofoil is worst for icing

A

Thin aerofoil

76
Q

What aircraft surface is most susceptible to icing

A

Tailplane because it’s a thin aerofoil

77
Q

What phase of flight is tailplane icing the biggest risk

A

Approach

= slow speeds, large downwash

78
Q

What effect could flaps have on the tailplane if it is iced

A

Flaps down = greater Downwash = greater AOA on tailplane = if iced could stall

79
Q

How to recover from a tailplane stall due to flaps in icing conditions

A

Return to previous flap setting

80
Q

What anti icing is left on permanently

A

Pitots

Pilot window (more stronger protection against bird strikes if warm)

81
Q

What is deformation

A

Damage twisting buckling

Changing shape

82
Q

What is degradation

A

Surface worn away over time

Solved by repainting

83
Q

Eqn for local speed of sound

A

39 squareroot temp in kelvin

84
Q

How to calculate the Mach cone angle

A

Sinangle = 1/Mach number

Or

Sinangle = LSS/TAS

ATPL POF (12 decks)

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